Question

What parts separate the anterior and medial compartments of the arm?

Answer 1

The arm is divided by a fascial layer (known as lateral and medial intermuscular septa) separating the muscles into two osteofascial compartments: the anterior and the posterior compartments of the arm.

The lateral intermuscular septum extends from the lower part of the crest of the greater tubercle of the humerus, along the lateral supracondylar ridge, to the lateral epicondyle; it is blended with the tendon of the deltoid muscle, gives attachment to the triceps brachii behind, and to the brachialis, brachioradialis, and extensor carpi radialis longus muscles in front. It is perforated by the radial nerve and profunda branch of the brachial artery.

The medial intermuscular septum, is thicker than the lateral intermuscular septum. It extends from the lower part of the crest of the lesser tubercle of the humerus below the teres major, and passes along the medial supracondylar ridge to the medial epicondyle; it is blended with the tendon of the coracobrachialis, and gives attachment to the triceps brachii behind and the brachialis in front. It is perforated by the ulnar nerve, the superior ulnar collateral artery, and the posterior branch of the inferior ulnar collateral artery.